Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 52
ler, will, as the ruler revolves around F, describe an hyperbola. To draw a tangent to any point of an hyperbola (Fig. 111). Let P be the point. On F P lay off P jt?, equal to F P ; draw the line Y p;from P let fall a perpendicular on this line, P p^ for the tangent. To describe a spiral (Fig. 112…
Mechanical drawing
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